build: Bump gdk version requirement
build: Bump gdk version requirement

gtk+-3.22.6 includes all the fixes required to use gdk subsurfaces under
Wayland, bump the minimal required version to this new version.

https://bugzilla.gnome.org/show_bug.cgi?id=774546

GNOME/clutter,GNOME/clutter,GNOME/clutter,GNOME/clutter,GNOME/clutter